This invention relates generally to a pressure regulator suitable for use with a variable output pump. More particularly, it relates to a pressure regulator including a control device, such as a step motor, servomotor or the like, which by controlling pump output precisely determines the pressure level at which the regulating function takes place.
A conventional pressure regulator typically includes a spring-biased valve against which is applied the force developed by a fluid pressure to be regulated. Some form of control device usually is provided for varying the spring force so that the point of equilibrium between the fluid and spring forces may be varied. By this means the pressure level at which regulation takes place is determined. In an environment where regulation is to function automatically, a motor-actuated control device typically is provided for varying the spring force. The motor generally must be heavy to insure that an adequate spring force is developed.
A step motor basically is a DC motor which rotates in specific increments or steps. Such a motor, if not overloaded, can run in the open loop mode without missing a step. One needs only keep track of the number and direction of steps taken in order to know the precise position of the rotor at all times.
A step motor could be used to precisely vary the spring force in a conventional pressure regulator. However, it would require a heavy, expensive step motor to compress the spring. As a step motor typically has low torque capacity, it would be desirable to minimize the load on the step motor in order to obtain the highest step rates with the lowest cost motor.
U.S. application Ser. No. 452,551 filed Dec. 23, 1982 is of common assignee herewith and is incorporated herein by reference. That application discloses a step motor-controlled pressure regulator having good response characteristics, stable operation and low cost. The pressure regulator represents an advance in the art, but is suited for use with a fixed output pump. Thus there remains a need in the art for a comparable pressure regulator which is suitable for use with a variable output pump.